Several ocular diseases and conditions can be treated through the administration of active agents, such as pharmaceuticals. For example, retinal diseases including diabetic retinopathy, age-related macular degeneration (AMD) and macular edema can be treated pharmacologically. Furthermore, conditions related to ocular surgery, such as inflammation, infection, and the like can be treated pharmacologically.
However, due to anatomical factors, it is very challenging to deliver an effective concentration of a pharmacologically active agent to interior portions of the eye, particularly when the pharmacologically active substance needs to be administered over an extended period of time.
Various methods have been developed for delivering an active agent to the interior segments of the eye, but all have disadvantages. One currently used method to treat intraocular conditions is delivering the active agent topically to the cornea or sclera. Topical drug delivery is disadvantageous for intraocular portions of the eye, such as the posterior chamber, because the drug must penetrate several layers of tissue before reaching the target area.
Another method for intraocular delivery of an active agent is transcleral delivery, in which the pharmacological agent is introduced through the choroidal blood supply. Similar to topical delivery, transcleral delivery requires that the active agent penetrate several layers of tissue to reach target areas, such as the retina. Furthermore, when treating locations such as the retina, this and other systemic delivery methods must cross the blood/retina barrier, which is disadvantageous because of the relative impermeability of the blood-retina barrier.
The most typical currently-used method to apply a given active agent to the interior of the eye is repeated intravitreal injections. These repeated intravitreal injections are quite uncomfortable for the patient, which leads, in part, to a decrease in patient compliance. Moreover, repeated intravitreal injections carry an increased risk of local side effects and complications, such as corneal abrasions and infection. Attempts to develop methods of avoiding intravitreal injections have also typically presented significant disadvantages.
For example, U.S. Patent Application publication No. 2004/0133155, to Varner et al., discloses devices, such as scleral plugs, for intraocular drug delivery that generally include a coil shaped implant that is positioned in the posterior chamber of the eye with a cap residing outside of the eye.
Further, U.S. Patent Application publication No. 2002/0188282, to Greenberg, discloses implantable drug delivery devices that include an electrode array body in communication with a drug reservoir positioned outside of the eye.
However, a particular disadvantage of drug delivery systems having portions of the systems residing outside of the eye is patient discomfort, and additional disadvantages include increased risk of complications and side effects, such as infection.
Therefore, a need exists to develop alternative systems and methods to deliver an active agent to the internal portions of the eye, particularly when the biologically active agent needs to be administered over an extended period of time.